The present invention relates to compositions comprising methylene chloride, which are stabilized in order to avoid the decomposition of the methylene chloride during its storage or during its use, and which are particularly suitable for aerosols.
Methylene chloride is frequently used in aerosol compositions as a solvent for the active materials, and as a depressant for the propellant (dichlorodifluoromethane, butane, propane, carbon dioxide, nitrous oxide and the like). However, methylene chloride tends to decompose, especially in contact with metallic surfaces and under the action of heat. The resulting corrosion of the metallic surfaces becomes particularly great when the aerosol compositions contain water in addition to the methylene chloride. This corrosiveness of methylene chloride is in particular very marked towards metals frequently used in the manufacture of aerosol cans, such as aluminum or tinplate.
It has already been proposed to counteract the damage to metallic surfaces by the halogenomethanes by adding to the latter small amounts of a stabilizer of an organic nature. Among the stabilizers which have been proposed for stabilizing chloromethanes such as methylene chloride, there may be mentioned various substances such as amylene (U.S. Pat. No. 1,904,450 in the name of DU PONT DE NEMOURS, filed on Mar. 3rd, 1931), phenol (U.S. Pat. No. 2,008,680 in the name of DU PONT DE NEMOURS, filed on Mar. 3rd, 1931), nitrated compounds (British Pat. No. 773,187, filed on Dec. 8th, 1955 in the name of FARBWERKE HOECHST AG), dimethoxymethane (Belgian Pat. No. 741,556, filed on Nov. 12th, 1969 in the name of DOW CHEMICAL CO.) and epoxides (U.S. Pat. No. 2,106,158 in the name of I. G. FARBEN, filed on July 4th, 1935).
The addition of these products to methylene chloride, however, does not make it possible to avoid the corrosion of the metallic surfaces when the methylene chloride is used as a mixture with water.
To overcome this disadvantage, it has been proposed to use synergistic mixtures of stabilizers. Among the mixtures of stabilizers which have been proposed for stabilizing methylene chloride, there may be mentioned the mixtures of 2-methylfuran with epoxides (Belgian Pat. No. 781,796, filed on Apr. 7th, 1972 in the name of SOLVAY & Cie.). These mixtures have provided particularly efficient for stabilizing methylene chloride in the presence of small amounts of water, of approximately a few percent relative to the methylene chloride. However, they do not make it possible to stabilize the methylene chloride sufficiently if it is stored in the presence of larger amounts of water.